Current conventional high-field magnetic resonance imaging (MRI) systems are not suitable for use in a typical doctor's office or in a mobile medical facility. A typical imaging system requires a large magnetic field (about 1 Tesla) that can be only achieved by operation of a large superconducting magnet at liquid helium temperature (about 4 K). Operation of the large field magnet at such temperature requires a special, dedicated facility such as a secured shielded room, a control room and an equipment room. This kind of arrangement is not easily affordable by a doctor. Therefore, it makes the system largely unavailable to disadvantaged populations. Other technical disadvantages are severe image distortions with in-vivo metallic implants and difficult intraoperability (e.g., imaging during surgery). Accidents associated with magnetic projectiles (a chair, an oxygen tank, etc) have also been reported.
Low field NMR using a superconducting quantum interference device (SQUID) detector, also known as SQUID NMR, has been recently used to study material properties. SQUID NMR techniques have also been applied to MRI imaging at low field, thus showing that superconducting magnets are not necessary for imaging. In addition, low field MRI showed an improved contrast imaging capability not achievable by conventional MRI. However, current low field SQUID MRI devices still require liquid helium cryogen service to operate the SQUID detector and the pick-up coil. Moreover, the imaging scanning time is too long. Also, the existing laboratory-based prototypes are designed with no transportability and intra-operability.